Multiple 5V 0.27A Fans with 12V supply?

Other Hardware Motors, Mechanics, Power and CNC
1

Hi, I want to control multiple (like 5?) fans with an arduino/microcontroller.

I started with wanting to control multiple 12V fans, and so I figured the way to go was like this, where I connect the black wire of each fan to the drain of the mosfet, the source to GND, the gate to a 220ohm resistor and then to a PWM pin of the arduino. I got a 12V 2A power supply for all this.

Now I found this 5V fan, which feels stronger in wind than my 12V test fan, so I'd like to use it instead. Anyways, I got stuck thinking about how to power these. The Arduino doesn't provide enough current (0.4A only?) to power it, but my power supply has too much voltage.

My questions:

  • Will too much voltage from the 12V power supply fry the 5V fans?
  • If I connect the 12V supply to the barreljack of the arduino, will it provide more current to power the 5V fans from the 5V pin?
  • Any tips how to go best about powering the fan installation?
  • Or should I just get a 5V 2A power supply?
2

You cannot use the Arduino to power any fan.

You must have a separate power supply to suit the fans you use . The Arduino can switch them via a transistor .

3

There's no way to understand from your description if your fans are rated at 5V or 12V.
And arduino is not a power supply.

4

Actually, that is your only choice.

5

My first option fans were 12V, so I got a 12V power supply for this.
The new one (which I linked) is 5V.
My question is about multiple 5V fans.
I'm wondering if I can use my 12V power supply to power the 5V fans.

6

See post #4

7

Do I still need a mosfet for this?

8

No, you control the speed using the fan PWM signal input.

9

You shouldn't do that. When the MOSFET is off you have 12V on the fan positive wire and the Arduino PWM pin connected to the fan, with nothing on the fan negative connection. You have a path for current from 12V through the fan to the Arduino. If you have not damaged it consider yourself lucky.

Edit:
See reply #10 and #15

1 Like
10

Oh. How then to do it?

I was thinking this for the 12V fan:

12v.HEIC
12v.HEIC1897×1913 879 KB

And then this for the 5V one:

5v.HEIC
5v.HEIC1667×1827 677 KB

11

You can use 12V to 5V step down converter, but honestly, doesn't make sense to me.
5V2A power supply doesn't really cost more and most of people have those laying around (usb chargers).

12

You just connect the fan to the power supply and write pwm-pin low when you want to stop the fan.

13

@kmin:
You just connect the fan to the power supply and write pwm-pin low when you want to stop the fan.

So is my drawing okay for that? Yellow is the PWM wire, so I just connect that one to the arduino and leave the blue out.

14

Yes.

1 Like
15

Thanks for the schematic, perfect example of why we ask people to post one at the start of a topic. From your initial description I thought your 12V fan had 3 wires: Positive, negative and PWM. Your schematic for the 12V fan is much clearer than your description. Your schematic for 12V is fine, you can do that.

For the 5V fan that also looks OK, although I'm not sure of the function of the yellow and blue wires.

1 Like
16

Thanks! Yellow is pwm, blue is tach.

1 Like
17

NO.
The BLUE wire is for PWM input to the fan
No need for the diode.

NOTE:

  1. LEAD WIRE 1571 28AWG
    RED WIRE --------- （ + ）(3)
    BLACK WIRE --------- （--） (4)
    YELLOWER WIRE ----------- (FG) (2)
    BLUE WIRE---------- (PWM) (1)
  2. 导线框外线长：150mm
2 Likes
18

Now all you need is the code for generating the 25kHz PWM for the fan.

2 Likes
19

Thanks!
In the 12V scheme I do need a diode right?
Why is this not needed anymore in the 5V scheme?

20

Yes

Why is this not needed anymore in the 5V scheme?

The diode is there to protect the MOSFET from voltage spikes but with the 5V fan there is no MOSFET.